<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <div id="app">
    也许是天气，也许是...
    {{ msg }}
  </div>

  <script type="module">
    import { createApp, ref } from 'https://unpkg.com/vue@3/dist/vue.esm-browser.js'

    let app = createApp({
      setup() {
        return {
          msg: ref('还是天气')
        }
      }
    }).mount('#app')
  </script>
</body>

</html>